Varies as far as where to hook up your hoses on equipment.
But the idea is...
Discharge of recovery unit to Equipment Pressure Port/Service Valve
Suction of recovery unit to vapor side of recovery tank(s)
Liquid side of recovery tanks to another service valve
DIscharge of recovery unit "pushes" vapor into unit allowing liquid to be "pulled" into recovery tank
Isolating where the liquid will be is the key.
If you have a real cold evap coil... then try to push on one side and pull out the other.
If you pumped the liquid into the condenser coil (or the condenser coil is in a colder environment than the evap)... then push on one side and pull out the other.
Once you can't move any more liquid... you'll have to revert to the standard way of suckin out the vapor.
Otherwise you'll be recirculating vapor hehe.